Propulsion nozzle and actuator system employed therein

ABSTRACT

A propulsion nozzle is described in combination with a gas turbine engine. The hot gas stream of the engine is discharged through the nozzle for forward propulsion, or may be discharged laterally thereof for reverse thrust. The nozzle is of the variable geometry, plug type wherein flaps are pivotal to vary the discharge and throat areas thereof for different flight conditions spanning subsonic and supersonic operation. The flaps for controlling discharge area are pivotally mounted on a frame which is longitudinally displacable to uncover ports in the sides of the pod or nozzle structure. The hot gas stream may then be laterally and forwardly discharged therethrough for reverse thrust. Axial movement of this frame is controlled by a set of first actuators. Pivotal movement of the flap is controlled by a set of second actuators. The first and second set of actuators are sequentially interconnected in such a fashion that both sets may be powered from a single source of pressurized hydraulic fluid through &#39;&#39;&#39;&#39;hard&#39;&#39;&#39;&#39; conduits. Valves are employed to enable independent operation of each set of actuators in providing the varying thrust capabilities of the nozzle.

[111 3,831,493 Aug. 27, 1974 PROPULSION NOZZLE AND ACTUATOR SYSTEMEMPLOYED THEREIN [75] Inventor: Robert Price Wanger, Fairfield,

Ohio

[73] Assignee: General Electric Company, Lynn,

Mass.

221 Filed: Sept. 13,1973

21 Appl. No.: 396,985

Related US. Application Data [62] Division of Ser. No. 264,394, June 19,1972.

Primary ExaminerEdgar W. Geoghegan Assistant ExaminerA. M. Zupcic [5ABSTRACT A propulsion nozzle is described in combination with a gasturbine engine. The hot gas stream of the engine is discharged throughthe nozzle for forward propulsion, or may be discharged laterallythereof for reverse thrust. The nozzle is of the variable geometry, plugtype wherein flaps are pivotal to vary the discharge and throat areasthereof for different flight conditions spanning subsonic and supersonicoperation. The flaps for controlling discharge area are pivotallymountedon a frame which is longitudinally displacable to uncover portsin the sides of the pod or nozzle structure. The hot gas stream may thenbe laterally and forwardly discharged therethrough for reverse thrust.Axial movement of this frame is controlled by a set of first actuators.Pivotal movement of the flap is controlled by a set of second actuators.The first and second set of actuators are sequentially interconnected insuch a fashion that both sets may be powered from a single source ofpressurized hydraulic fluid through hard" conduits. Valves are employedto enable independent operation of each set of actuators in providingthe varying thrust capabilities of the nozzle.

8 Claims, 8 Drawing Figures This is a division of application Ser. No.264,394, filed June 19, 1972.

The present invention relates to improvements in propulsion nozzles,particularly of the type having supersonic capabilities and used incombination with gas turbine engines in the propulsion of aircraft, andfurther to improved hydraulic systems employed therein.

Many problems exist and have long been recognized in aircraft propulsionsystems having supersonic capabilities. For practical purposes it may beconsidered that, for supersonic propulsion, a convergent-divergentpropulsion nozzle is a necessity. For subsonic operation a convergentnozzle is required for efficient operation. Since the subsonic portionof an overall flight regime may equal, or often exceed, the supersonicportion, a convergent nozzle configuration also becomes a practicalnecessity by reason of the economies to be derived therefrom.

Many different nozzles have been proposed, and several previouslyutilized, to obtain both convergent and convergent-divergentconfigurations for different flight conditions from subsonic throughsupersonic. Such nozzles mostly incorporate pivotal flaps and arecommonly referred to as variable geometry nozzles.

Another problem in basic nozzle configuration is maintaining a minimumlength. it has previously been recognized that the use of a central plugcan shorten the overall nozzle length and thus plug nozzles and variablegeometry, plug nozzles have been developed toward the general end ofproviding for the different flight conditions as well as reducingoverall nozzle length.

Beyond this, I nozzle constructions become further complicated inproviding reverse thrust capabilities as is particularly required incommercial aircraft. These complications are due to the fact thatreverse thrust is most effectively attained by diverting the hot gasstream, employed for forward propulsion, in a lateral and forwarddirection and the further fact that such diversion must be done in thegeneral area of the propulsion nozzle.

One solution to these overall problems is to pivotally mount flaps,which define the discharge area of the nozzle, on a frame which isaxially displaceable to uncover lateral discharge ports, through whichthe hot gas stream of the engine may be discharged for reverse thrust.Such a configuration however, poses particular problems in controllingthe pivotal positions of the flaps for varying operating conditions offorward propulsion. and also displacing this frame to provide thereverse thrust capability.

While cylinder type actuators provide an obvious expedient forcontrolling movement of the nozzle frame and flaps, the adverseenvironment of the propulsion nozzle, subject to gas stream temperaturesin excess of 2000 Fahrenheit, militates against incorporation of anyconventional actuator system. This becomes more apparent upon furtherappreciation of the fact that it is required or desired to positivelydisplace the frame, on which the flaps are mounted, through asubstantial distance, as well as to positively and independently pivotthe flaps relative to such frame. Any known conventional system ofactuators would involve the use of flexible conduits for the pressurizedmotive fluid for the actuators. Such flexible conduits, while basicallysound in principle, do not approach the degree of reliability,simplicity, and compactness of hard conduits, particularly when carryingpressurized hydraulic motive fluid and operating under such adverseenvironmental conditions of extreme temperatures, and also vibration.

Accordingly, one object of the present invention is to provide animproved propulsion nozzle having pivotal flaps to accommodatesupersonic and subsonic operation as well as having provision forreverse thrust capability and in so doing to provide for positivecontrol of the component parts of such a nozzle through an actuatorsystem which eliminates any requirement for flexible conduits carryingpressurized motive fluid for the actuators.

Another object of the present invention is to provide a hydrauliccontrol system for a propulsion nozzle wherein first and secondactuators, either individually or in sets thereof, are sequentiallyconnected for independent operation thereof, in controlling movement ofa propulsion nozzle frame and flaps mounted thereon, or for controllingmovement of other elements connected to such actuators.

These ends are broadly attained by a propulsion nozzle mountable at thedischarge of a gas turbine engine and comprising a pod structure havingdownstream extensions between ports for lateral discharge of hot gasduring thrust reversal. Downstream of these extensions is a frame onwhich are mounted flaps for controlling the discharge area of thenozzle. A central plug may also be provided and incorporate flaps forcontrolling the throat area of the nozzle.

A first set of actuators is mounted within the pod extensions foraxially translating the referenced frame to shift shroud means thereonbetween a forward thrust position wherein the reverse thrust ports areclosed and a reverse thrust position wherein these ports are open. Asecond set of actuators is mounted on this movable .frame forcontrolling the pivotal positions of the flaps and the discharge area ofthe nozzle.

The two sets of actuators are sequentially connected, from a relativelyfixed supply, for flow of pressurized fluid therethrough, in controllingtranslation of the frame and pivoting of the flaps. Valve means may beemployed to provide for energization of one set of flaps independentlyof the other. The connections between the actuators may provide for flowof'pressurized fluid as well as discharge of fluid to a drain or thelike, as in a closed hydraulic fluid pressurization system. Theinterconnection between the two sets of actuators are made betweenactuator components which are. connected to the noule frame so thatthere is no linear displacement and hard" conduits, or other rigidelements may be employed for greater reliability and other relatedadvantages.

in yet a broader sense of the invention, the two sets of actuators, orsingle actuators from each set may be interconnected ina similar fashionto control move ment of first and second members relative to each otherand to a fixed member.

The above and other related objects and features of the invention willbe apparent from a reading of the following description of the of thedisclosure found in the accompanying drawings and the novelty thereofpointed out in the appended claims.

In the drawings:

FIG. 1 is a diagramatic illustration of a gas turbine engine andpropulsion nozzle embodying the present invention;

FIG. 2 is an enlarged, longitudinal section of a portion of thepropulsion nozzle, positioned for supersonic propulsion;

FIG. 3 is a diagramatic illustration of a hydraulic system, employed inthe present invention in a position corresponding to FIG. 2;

FIG. 4 is a section similar to that of FIG. 2, but show ing the nozzlepositioned for subsonic operation;

FIG. 5 is a diagramatic illustration of the hydraulic system in aposition corresponding to FIG. 4;

FIG. 6 is a section also corresponding to that of FIG. 2, but showingthe nozzle positioned for reverse thrust;

FIG. 7 is a schematic view of the hydraulic system in I a positioncorresponding to FIG. 6; and

FIG. 8 is a section taken generally on line VIII-VIII in FIG. 2.

FIG. 1 illustrates a gas turbine engine 10 and a propulsion nozzle 12.The manner of mounting, i.e. the installation of, the engine 10 andnozzle 12 can vary widely between different types of aircraft. For sakeof illustration a relatively fixed pod structure 14 is shown, which maybe mounted on the aircraft by a pylon, or the like, not shown herein.The pod 14 would be compositely formed and define at one end the outerbounds of an inlet 16 which, for supersonic operation, may also includean axi-symmetrical spike 18. In supersonic operation, air entering theinlet 16 is shocked down to a subsonic velocity. Inlet air enters theengine compressor 20 and is pressurized and then discharged to acombustor 24 to support combustion of fuel in the generation of a hotgas stream. A portion of the energy of the hot gas stream is extractedby a turbine 26 to drive the rotor of the compressor 20 through a shaft27. The hot gas stream then flows to the nozzle 12 and the remainingenergy of the hot gas stream is converted to a propulsive force as it isdischarged therefrom.

Gas flow from the turbine 26 is defined, at its outer bounds, by acompositely formed casing 28 which, in

effect, is an extension of the engine casing 22, leading to the nozzle12. Within the discharge casing 28 and extending the length of thenozzle 12 is a plug 30 which is an aerodynamic component of the nozzle.The nozzle 12 is also of the variable geometry type comprising an outerset of flaps 32 and expansible flaps 34 on the plug 30. The nozzle 12 insupersonic operation is predominantly a convergent-divergent nozzle asis further illustrated in FIG. 2. The flaps 32 are pivoted to controlthe discharge area of the nozzle, and the flaps 34 are pivoted, in anexpansible fashion, to control the throat area of the nozzle, as taughtin US. Pat. No. 3,237,864 of common assignment. The flaps 32 and 34 arepivotal to aerodynamically form a convergent nozzle for subsonicpropulsion, FIG. 4.

The nozzle 12 also incorporates reverse thrust capabilities whereinnormal rearward discharge of the hot gas stream is blocked and directedlaterally and forwardly through ports 36 provided in the nozzlestructure. In forward propulsion these ports are covered by a shroud 38which is translated downstream for reverse thrust operation as willlater be'described in detail.

The compositely formed discharge duct 28 includes a pod frame member 42,(FIGS. 2, 4 and 6). A plurality of hollow extensions 44, see also FIG.8, project downstream from the frame 42 between the ports 36. The innersurfaces 46 of the extensions 44 and plates 48 define the outer boundsof the flow path of the hot gas stream leading to the throat of thenozzle 12. The plates 48 are secured to a frame (best shown in FIG. 6)50 to which the shroud 38 is also secured. Frame 50 is guided by theshroud 38 and extensions 44 for axial movement from the positionillustrated in FIG. 2 to the position illustrated in FIG. 6.

The axial movement of the frame 50 is controlled by a plurality ofactuators 52 which are disposed generally within the extensions 44 andthus protected from direct exposure to the hot gas stream passingthrough the nozzle 12. Three or more actuators 52 are preferablyemployed, each being mounted in selected, spaced extensions 44. However,for simplicity of description and illustration, a single actuator isshown in FIGS. 2, 4, 6 and 8, and only two of the actuators 52 are shownin the diagramatic views of FIGS. 3, 5 and 7. As will be seen from FIG.3, the actuators 52 comprise basic components including an outercylinder 54, a piston 56, slidable therein, and a piston rod 58extending, from one side of the piston 56, through the rod end of thecylinder adjacent the pod frame 42. The piston rods 58 are pivotallyattached to the pod frame 42 at 60. The cylinders 54 are pivotallyconnected to the nozzl frame 50 at 62.

Again referencing FIGS. 2 and 4 and the nozzle flaps 32, these flaps arepivotally mounted at 66 on the annular frame 50. The flaps 32 aregenerally triangular in shape, being feathered at their downstream ends,with their outer surfaces generally aligned with the pod structure forgood aerodynamic performance. The flaps 32 are pivotally positionedrelative to the frame 50 by a second set of actuators 68. Again aplurality of actuators 68 may be employed, generally three or more innumber. However, for sake of illustration, only one actuator 68 is shownin FIGS. 2, 4 and 6 and only two such actuators are illustrated in thediagramatic views of FIGS. 3, 5 and 7. The actuators 68 correspond tothe actuators 52 in each comprising a cylinder 70 within which rides apiston 72. A piston rod 74 extends from one side of the piston, beyondthe downstream end of the cylinder 70. The cylinders 70 are pivotallymounted on the frame 50 at 76 and the piston rods 74 are pivotallyconnected to a unison ring 78 at 80. Links 82 are pivotally connected attheir opposite ends to the unison ring 78 and each of the flaps 32 at84. It will be apparent that axial movement of the unison ring 78imparts pivotal movement to the flaps 32 as will be evidenced by acomparison of FIGS. 2 and 4.

Next to be described is the system for providing pressurized hydraulicfluid to the actuators 52 and 68 and thus controlling the position ofthe frame 50 and the flaps 32. Referencing first FIG. 3, apressurization conduit 86, at the fixed pod frame 42, is connected to anappropriate source of pressurized hydraulic fluid, as is commonly foundin such engines or in the aircraft system itself. The pressurizationconduit 86 is connected to a valve 88 which also has extending therefroma drain conduit 90 which is connected to the sump or drain side of thehydraulic pressurization system. A pair of conduits 92 and 94 extendfrom the opposite side of the valve 88 and are connected to plenumconduits 96 and 98 respectively. A conduit 100 connects each of theactuators 52 to the common plenum 96. More specifically, each of theconduits 100 extends to a port 104 formed in the piston rod 58, outsidethe cylinder 54, for connection with a passageway 106 extending axiallythrough the piston rod 58 to a port 108 adjacent the rod end side of thepiston 56. Conduits 102 extend respectively to a port 110 formed in eachpiston rod 58, outside the cylinder 54, and connect with a passageway112 extending axially through the piston rod 58 to a port 114 on thehead end side of the piston 56. For simplicity herein the end of thecylinder from which the piston rod 58 projects will be called the rodend." The rod ends of each of the cylinders 54 are interconnected byconduits 116 which in turn connect to a single or common conduit 118.The head ends of the cylinders 54 are interconnected by conduits 120which are jointed to a single or common conduit 122. Conduits 118, 122are connected to a valve 124 which is mounted on the nozzle frame 50.

The rod ends of the cylinders 70, of the actuators 68, areinterconnected by conduits 126 to a single or common conduit 128.Similarly the head ends of the cylinders 70 are interconnected byconduits 130 and connected to a single or common conduit 132. Theconduits 128 and 132 are in turn connected to the valve 124.

FIG. 3 illustrates the flow paths of hydraulic fluid through the valves88 and 124 to obtain the supersonic propulsion position illustrated inFIG. 2. Thus it will be seen that pressurized fluidflows sequentiallyfrom the conduit 86, through valve 88, conduit 92, plenum conduit 96,conduits 100, piston rod passageways 106 to pressurize the rod ends ofthe cylinders 54 and maintain the pistons and piston rods in theretracted positions. Sequential flow then continues from the rod ends ofthe cylinders through conduits 116, common conduit 118, valve 124,common conduit 128 to also pressurize the rod ends of the cylinders 70,thus maintaining the piston rods 74 in their retracted positions and theflaps 32 in their positions of maximum divergence illustrated in FIG. 2.Also, in this condition, the head ends of the cylinders 70 are connectedthrough conduits 130, common conduit 132, valve 124, common conduit 122and conduits 120 to the head ends of the cylinders 54, then through thepassageways 112, conduits 102 to the plenum conduit 98 and then backthrough the valve 88 to the drain conduit 90.

The valves 88 and 124 may take the form of servovalves, well known tothose skilled in the art, and would be controlled by signal imputs fromeither the pilot of the aircraft or from automatic controls which adjustthe nozzle geometry in accordance with the operating conditions of theaircraft engine and propulsion system in a known manner. Thus, forexample, in certain regimes it is desirable that the flaps 32 be swunginwardly under certain supersonic flight conditions, or wholly inwardlyas illustrated in FIG. 4 for subsonic propulsion. In either event thevalve 88 is maintained in its position illustrated in FIG. 3, and thenpressurized fluid from the common conduit 118 is switched by the valve124, see FIG. 5, to the common conduit 132 at the same time the commonconduit 128 is switched for connection with the common conduit 122. Thusthe head ends of the cylinders 70 are pressurized to extend the pistonrods 74 and displace the unison ring 78 in a downstream direction andpivot the flaps 32 to the position of FIG. 4. At the same time the rodends of the cylinders are drained, through the actuators 52, back to thedrain conduit 90. The servovalve 124 further has the capability, againknown to those skilled in the art, of

balancing pressures on opposite sides of the piston 72 to maintain it inan intermediate position within the cylinder to thus maintain the flaps32 also in intermediate positions.

Although not illustrated herein, it ws contemplated that, in accordancewith well known practices, synchronizing means would be employed tomaintain at all times uniform travel of the piston rods 58 and 74, suchmeans may take various forms such as worms and worm wheelsinterconnected by flexible cables. It will also be noted that theposition of the plug flaps 34 varies between FIGS. 2 and 4. Thisfunction forms no part of the present invention and may be accomplishedby means as taught in the previous referenced US. Pat. No. 3,237,864.

When reverse thrust is desired or required, the frame 50 is shiftedaxially downstream from the position of FIGS. 2 and 4 to the position ofFIG. 6. This is achieved by switching'flow through the valve 88. Whenthis is done, as indicated in FIG. 7, the common plenum 98 becomespressurized, directing pressurized fluid through the piston rodpassageways 112 to the head ends of the cylinders 54. At the same timethe common passageway or plenum passageway 96 is connected to thehydraulic system drain conduit and the rod ends of the cylinders 54 aredepressurized through rod passageways 106. The pistons 56 are displacedto extend the piston rods 58 and thereby displace the frame 50 in thedownstream position of FIG. 6.

When this occurs the shroud 38 and the plates 48 are displaced from theports 36 and the hot gas stream is then free to be dischargedtherethrough. For most effective reverse thrust operation, blockers 136are dis posed in the hot gas stream flow path at the downstream ends ofthe ports 36.-Further, louvers I40 may be placed in the discharge ports36 to better direct the hot gas stream in a forwardly direction toincrease reverse thrust capabilities. The blockers 136 may bemechanically linked to the frame 50 or otherwise actuated for deploymentin blocking relation, as described. Such means, however, form no part ofthe present invention.

If it is desired to maintain the flaps 32 in their inwardly swungpositions during reverse thrust operation, flow of pressurized fluidthrough the-valve 124 as is illustrated in FIG. 7. In this position,with the head ends of the cylinders 54 pressurized, pressurized fluidflows through the valve 124 to the head ends of the cylinders 70 so thatthe piston rods 74 are maintained in their extended positions. If thevalve 124 is not switched as shown in FIG. 7, the flaps 32 will be swungoutwardly. Additionally, the flaps could be maintained in their inwardpositions, when the frame 50 is so displaced, by shifting the valve to aposition wherein flow between the conduits 118, 122 and 128, 132 isblocked.

The described embodiment of the invention is highly effective inobtaining the desired control of the described propulsion nozzlecomponents for both supersonic, subsonic and reverse thrust operation.In so doing the actuators therefor are protected at all times from anysubstantial, direct exposure, to the extremely high elevatedtemperatures of the gas stream. Further, these ends are accomplished ina manner which enables *hard" conduits to be employed. Hard conduit, asused herein, includes both passageways formed in rigid members such asthe piston rod passageways 106, 112,

as well as separate conduit elements formed of relatively rigid integraltubing commonly used to transmit high pressure fluids. In particular,with regard to this aspect of the invention, it will be noted that noneof the conduits employed herein extend between components which haverelative linear movement therebetween. The only such relative movementis only a very minimal pivotal movement as found in the common conduits128 and 132 which extend between the pivotal cylinders 70 and therelatively fixed valve 124. However, the extent of such motion ormovement is nominal and may be readily taken by hard conduit tubingwithout the necessity of so called, compositely, formed flexibleconduits. All of this gives a high degree of reliability to the nozzlesystem and the hydraulic components thereof.

While uniquely related to the described propulsion nozzle, it will beappreciated that, in the broader aspect of the invention, the hydraulicsystem herein has further utility both in the general field ofpropulsion nozzles and in other fields where hydraulic actuation systemsrequiring a great degree of flexibility, and further requiring theelimination of flexible interconnecting conduits, is required ordesirable. Additionally, it would be appreciated that some of thevalving means described herein could be simplified or eliminated wherethe pressurized motive fluid is not recycled, as for example, inpneumatic systems. The spirit and scope of the present inventiveconcepts is therefor to be derived solely from the following claims.

Having thus described the invention, what is novel and desired to besecured by LettersPatent of the United States is: a

1. An actuator system comprising a relatively fixed member,

first and second movable members,

first and second actuators, each having a cylinder element and a pistonelement means connecting the elements of said first actuator,

respectively, to said fixed member and said first movable member,

means connecting the elements of said second actuator, respectively, tosaid first and second movable members, and

passageway means, connectable with a source of pressurized motive fluidat said fixed member, and extending from said fixed member, through thefirst actuator element connected thereto, through the other firstactuator element and through the second actuator element connected tothe first movable member for sequential flow of motive fluid in poweringsaid actuators.

2. An actuator system as in claim 1 wherein the first and secondactuators extend in opposite directions from said first movable member,

3. An actuator system as in claim 1 wherein said passageway meansfurther include means connectable with a drain passageway, at said fixedmember, and extending from said fixed member through the first actuatorelement and through the second actuator element connected to the firstmovable member for sequential drain flow of mo tive fluid in poweringsaid actuators.

4. An actuator system as in claim 1 wherein a first valve is mounted onthe fixed member and connected on one side with pressurization and drainconduits the passageway means include passageways respectively extendingfrom opposite ends of said first actuator cylinder element, through theactuator element connected to said first movable member, to said valve,and

passageway means extending from opposite ends of the second actuatorcylinder element, through the second actuator element connected to saidfirst movable member, to said valve, said valve having means forselectively connecting different ends of said first and second actuatorcylinder elements therethrough.

5. An actuator system as in claim 1 wherein,

the cylinder elements of the first and second actuators comprisecylinders having at one end a head end and the piston elements comprisepistons slidable in the respective cylinders and having rods extendingtherefrom through the opposite, rod ends of the cylinders,

a first valve is mounted on the fixed member with pressurization anddrain conduits connected to one side thereof,

the first actuator piston rod is connected to the fixed member and hasfirst and second passageways extending longitudinally thereof from portsoutside its cylinder to ports respectively opening on opposite sides ofits piston adjacent thereto.

conduits respectively connect the outside ports of said first and secondpassageways to said first valve,

a second valve is mounted on said first movable member,

conduits respectively connect the rod and head ends of said firstactuator cylinders to one side of said second valve,

the second actuator cylinder is connected, at its head end to said firstmovable member,

conduits respectively connect the rod and head ends of said secondactuator cylinders to the other side of said second valve,

said first valve being selectively positioned to connect the first andsecond piston rod passageways with this pressurization and drainconduits to power the first actuator in opposite directions,

said second valve being selectively positioned to respectively connectthe ends of the first actuator with either of the ends of the secondactuator to power the second actuator in opposite directionsindependently of the first actuator and thereby impart relative movementbetween the first and second movable members.

6. An actuator system as in claim 5 wherein the actuators are disposedon opposite sides of the first movable member and their axes aregenerally parallel.

7. An actuator system as in claim further comprisa plurality of parallelfirst actuators, each constructed and connected to the fixed and firstmovable members as defined with respect to the first, first actuator,

a plurality of parallel, second actuators, each constructed andconnected as defined with respect to the first, second actuator,

first and second plenum conduits respectively connected to said firstvalve,

conduits respectively connecting the outside ports of said first andsecond piston rod passageways with the respective plenum conduits,

second actuators are generally parallel.

1. An actuator system comprising a relatively fixed member, first andsecond movable members, first and second actuators, each having acylinder element and a piston element means connecting the elements ofsaid first actuator, respectively, to said fixed member and said firstmovable member, means connecting the elements of said second actuator,respectively, to said first and second movable members, and passagewaymeans, connectable with a source of pressurized motive fluid at saidfixed member, and extending from said fixed member, through the firstactuator element connected thereto, through the other first actuatorelement and through the second actuator element connected to the firstmovable member for sequential flow of motive fluid in powering saidactuators.
 2. An actuator system as in claim 1 wherein the first andsecond actuators extend in opposite directions from said first movablemember.
 3. An actuator system as in claim 1 wherein said passagewaymeans further include means connectable with a drain passageway, at saidfixed member, and extending from said fixed member through the firstactuator element and through the second actuator element connected tothe first movable member for sequential drain flow of motive fluid inpowering said actuators.
 4. An actuator system as in claim 1 wherein afirst valve is mounted on the fixed member and connected on one sidewith pressurization and drain conduits the passageway means includeseparate passageways extending from the other side of said valve,through the first actuator element connected to the fixed member,respectively, to opposite ends of the first actuator cylinder element,said first valve being positioned to connect the drain andpressurization conduits respectively with either of said separatepassageways, a second valve is mounted on said first movable member, thepassageway means include passageways respectively extending fromopposite ends of said first actuator cylinder element, through theactuator element connected to said first movable member, to said valve,and passageway means extending from opposite ends of the second actuatorcylinder element, through the second actuator element connected to saidfirst movable member, to said valve, said valve having means forselectively connecting different ends of said first and second actuatorcylinder elements therethrough.
 5. An actuator system as in claim 1wherein, the cylinder elements of the first and second actuatorscomprise cylinders having at one end a head end and the piston elementscomprise pistons slidable in the respective cylinders and having rodsextending therefrom through the opposite, rod ends of the cylinders, afirst valve is mounted on the fixed member with pressurization and drainconduits connected to one side thereof, the first actuator piston rod isconnected to the fixed member p1 te firt acuatorpistn ro is on9memberand has first and second passageways extending longitudinally thereoffrom ports outside its cylinder to ports respectively opening onopposite sides of its piston adjacent thereto, conduits respectivelyconnect the outside ports of said first and second passageways to saidfirst valve, a second valve is mounted on said first movable member,conduits respectively connect the rod and head ends of said firstactuator cylinders to one side of said second valve, the second actuatorcylinder is connected, at its head end to said first movable member,conduits respectively connect the rod and head ends of said secondactuator cylinders to the other side of said second valve, said firstvalve being selectively positioned to connect the first and secondpiston rod passageways with this pressurization and drain conduits toPower the first actuator in opposite directions, said second valve beingselectively positioned to respectively connect the ends of the firstactuator with either of the ends of the second actuator to power thesecond actuator in opposite directions independently of the firstactuator and thereby impart relative movement between the first andsecond movable members.
 6. An actuator system as in claim 5 wherein theactuators are disposed on opposite sides of the first movable member andtheir axes are generally parallel.
 7. An actuator system as in claim 5further comprising a plurality of parallel first actuators, eachconstructed and connected to the fixed and first movable members asdefined with respect to the first, first actuator, a plurality ofparallel, second actuators, each constructed and connected as definedwith respect to the first, second actuator, first and second plenumconduits respectively connected to said first valve, conduitsrespectively connecting the outside ports of said first and secondpiston rod passageways with the respective plenum conduits, conduitsrespectively interconnecting the rod ends and head ends of the firstactuator cylinders, common conduits respectively connecting theinterconnecting conduits to said second valve, conduits respectivelyinterconnecting the rod and head ends of said second actuator cylinders,and common conduits respectively connecting the second actuatorinterconnecting conduits to said second valve.
 8. An actuator system asin claim 7 wherein the first and second actuators are disposed onopposite sides of said first movable member and the axes of the firstand second actuators are generally parallel.